1. Field of the Invention
The present invention relates to a thread guide device for a sewing machine comprising thread transfer means for transferring an upper thread to the vicinity of a needle eye, and threading means for inserting, into the needle eye, the upper thread transferred to the vicinity of the needle eye by the thread transfer means.
2. Description of the Related Art
Conventionally, JP-A-11-179084 and JP-A-11-267383 have disclosed a sewing machine comprising an automatic thread guide device for automatically delivering an upper thread to the vicinity of a needle eye and inserting the upper thread through the needle eye, for example.
An embroidering sewing machine described in the JP-A-11-179084 comprises thread delivery means for delivering an upper thread to be overhung from the upper part of the sewing machine to the vicinity of the eye of a sewing needle, and threading means for inserting the upper thread delivered by the thread delivery means into the eye of the sewing needle. The thread delivery means includes a thread delivery arm to be rotated by half, and the thread delivery arm is provided with a thread delivery holding portion for holding the upper thread. The thread delivery arm is rotated by half so that the thread delivery holding portion is reciprocated between the standby position of the upper part of the sewing machine and the vicinity of the sewing needle.
In a thread guiding operation to be carried out until the upper thread is inserted through the eye of the sewing needle, first of all, the upper thread is held by the thread delivery holding portion moved to the standby position of the upper part of the sewing machine so that the upper thread is held. At this time, the holding force of the thread delivery holding portion is reduced such that the upper thread can easily be set.
When the upper thread is held by the thread delivery holding portion, the thread delivery arm is rotated by half and the thread delivery holding portion is moved to the sewing needle with the upper thread held therein. When the thread delivery arm is to be rotated by half, the thread delivery holding portion is set to have great holding force such that the upper thread does not slip off.
When the thread delivery holding portion is moved to such a position that the upper thread is overhung toward the eye of the sewing needle, the upper thread is inserted through the eye of the sewing needle by the threading means. At this time, the thread delivery holding portion has the holding force reduced such that the upper thread can be removed from the thread delivery holding portion after the threading.
Then, the thread delivery arm is rotated reversely so that the thread delivery holding portion is moved from the sewing needle side toward the standby position. Thus, the thread guiding operation of the upper thread is completed.
In the conventional sewing machine, however, holding force of the thread delivery holding portion cannot be changed when the thread delivery arm is rotated by half to move the thread delivery holding portion from the standby position to the vicinity of the sewing needle and to move the thread delivery holding portion from the sewing needle side to the standby position. Therefore, in the case in which the thread remains in the thread delivery holding portion after the threading, there is a possibility that the thread delivery holding portion might strongly hold and pull up a thread and remove the thread from the eye of the sewing needle and the thread cannot be consequently guided with high precision.
Moreover, when the thread delivery holding portion is moved from the standby position to the vicinity of the sewing needle, the holding force of the thread delivery holding portion is reduced. In order to guide the thread with higher precision, it is more preferable that the holding force of the thread delivery holding portion should be properly adjusted into appropriate holding force during upper thread setting or threading.
In order to guide the thread with higher precision, moreover, it is preferable that the stop position of the thread delivery holding portion in the standby position should be placed to reliably set the upper thread into the thread delivery holding portion or the stop position of the thread delivery holding portion in the vicinity of the sewing needle should be placed to carry out the threading well.
It is an object of the invention to provide a thread guide device for a sewing machine which can carry out a thread guiding operation with higher precision.
In order to attain the object, as shown in FIGS. 1, 2, 9 and 12, for example, a first aspect of the invention is directed to a thread guide device (1) for a sewing machine comprising:
thread transfer means (10) including a thread holding portion (a thread holding portion 30) capable of holding an upper thread and serving to hold the upper thread in a thread holding position by means of the thread holding portion and to transfer the upper thread to the vicinity of a needle eye (N);
threading means (50) for inserting, into the needle eye, the upper thread (A) transferred to the vicinity of the needle eye by the thread transfer means; and
holding pressure changing means (a transfer cam 19, a holding pressure switching roller 46, a holding pressure switching operating plate 40, a holding pressure switching adjusting plate 42, a holding pressure switching link 43, a holding pressure switching plate 44) for changing a holding pressure of the thread holding portion during transfer in which the upper thread is to be transferred from the thread holding position to the vicinity of the needle eye and during return in which the thread holding portion is to be returned to the thread holding position after the upper thread is transferred to the vicinity of the needle eye.
According to the first aspect of the invention, the thread guide device for a sewing machine comprises the holding pressure changing means. Therefore, the holding pressure of the thread holding portion can be changed during the transfer in which the upper thread is to be transferred from the thread holding position to the vicinity of the needle eye and during the return in which the upper thread is to be transferred to the vicinity of the needle eye and the thread holding portion is to be then returned to the thread holding position.
Accordingly, it is possible to set that the holding pressure of the thread holding portion is increased during the transfer and the upper thread is prevented from slipping off from the thread holding portion, and the holding pressure of the thread holding portion is reduced during the return and the thread holding portion holds the upper thread without a pull even if the upper thread remains in the thread holding portion after threading. Thus, it is possible to carry out a thread guiding operation with higher precision.
As shown in FIG. 2, for example, a second aspect of the invention is directed to the thread guide device for a sewing machine according to the first aspect of the invention, wherein the thread transfer means includes the thread holding portion and a thread transfer member (20) for reciprocating the thread holding portion between the thread holding position and the vicinity of the needle eye by a rotation, and
the holding pressure changing means includes:
a rotor (a transfer cam 19) having two different cams (19b, 19c) from each other and rotated relatively with respect to the thread transfer member around a rotating shaft (a shaft 18) of the thread transfer member during the rotation of the thread transfer member;
a contact (a holding pressure switching roller 46) provided in the thread transfer member and coming in contact with the cams of the rotor rotated relatively with respect to the thread transfer member; and
holding pressure switching means (holding pressure switching operating plate 40, holding pressure switching adjusting plate 42, a holding pressure switching link 43, a holding pressure switching plate 44) for switching the holding pressure of the thread holding portion based on a displacement in a position of the contact which comes in contact with the cams.
According to the second aspect of the invention, the holding pressure changing means includes the rotor, the contact and the holding pressure switching means. Therefore, when the contact comes in contact with the thread transfer member along the cam of the rotor rotated relatively during the rotation of the thread transfer member, the position of the contact is changed so that the holding pressure of the thread holding portion is switched based on a displacement in the position of the contact.
Accordingly, when the thread transfer member is rotated so that the thread holding portion is reciprocated between the thread holding position and the vicinity of the needle eye, the holding pressure of the thread holding portion can be switched.
A third aspect of the invention is directed to the thread guide device for a sewing machine according to the second aspect of the invention, further comprising contact cam switching means (a compression spring 47, a tension spring 48, an inclined portion 19h) for switching the cam with which the contact comes in contact when the thread holding portion goes from the thread holding position to the vicinity of the needle eye and when it comes back from the vicinity of the needle eye to the thread holding position.
According to the third aspect of the invention, the thread guide device for a sewing machine comprises the contact cam switching means. Therefore, the cam with which the contact comes in contact is switched when the thread holding portion goes and when it comes back. For this reason, the contact comes in contact with the different cams when the thread holding portion goes and when it comes back. Therefore, the holding pressure to be switched by the holding pressure switching means is varied when the thread holding portion goes and when it comes back. Thus, it is possible to change the holding pressure of the thread holding portion when the thread holding portion goes and when it comes back.
A fourth aspect of the invention is directed to the thread guide device for a sewing machine according to the first aspect of the invention, wherein the thread transfer means includes a thread transfer member having the thread holding portion and supported rotatably, and
a rotor capable of being rotated around a rotating shaft of the thread transfer member and capable of being at least partially (a stopper 19d) engaged with at least a part (an abutment portion 26a) of the thread transfer member, and holding a state in which a rotation is not carried out in engagement with the thread transfer member, thereby stopping the thread holding portion in the thread holding position,
the thread guide device further comprising:
engagement position changing means (a positioning plate 26) capable of changing an engagement position of the rotor and the thread transfer member.
According to the fourth aspect of the invention, the thread guide device for a sewing machine comprises the engagement position changing means. Therefore, the engagement position of the rotor and the thread transfer member is changed so that the relative position of the rotor and the thread transfer member in a state in which the rotor is engaged with the thread transfer member can be varied. By holding such a state that the rotor is not rotated in engagement with the thread transfer member, consequently, it is possible to change a position in which the thread holding position stops.
More specifically, it is possible to change the engagement position of the rotor and the thread transfer member, thereby regulating the stop position of the thread holding portion. Consequently, the thread holding portion can be set into such a position that the upper thread can easily be held. Accordingly, it is possible to carry out the thread guiding operation with higher precision.
A fifth aspect of the invention is directed to the thread guide device for a sewing machine according to the second aspect of the invention, wherein the holding pressure switching means is a link device including a plurality of links, and
there is provided fulcrum position changing means (a holding pressure switching adjusting plate 42) capable of changing fulcrum positions of the links (a holding pressure switching link 43).
According to the fifth aspect of the invention, the thread guide device for a sewing machine comprises the fulcrum position changing means. Therefore, it is possible to change the fulcrum position of the link of the holding pressure switching means. Consequently, it is possible to vary a degree at which a displacement in the position of the contact is switched into the thread holding pressure. Thus, it is possible to regulate the holding pressure of the thread holding portion in addition to the switching of the holding pressure by the cam of the rotor.
Accordingly, the holding pressure of the thread holding portion can be finely regulated by changing the fulcrum position of the link through the fulcrum position changing means. For example, accordingly, a holding pressure applied during the threading by the threading means can be regulated into a proper holding pressure so that the thread guiding operation can be carried out with higher precision.
A sixth aspect of the invention is directed to the thread guide device for a sewing machine according to the second aspect of the invention, further comprising contact position determining means (a holding pressure switching abutment plate 6) capable of determining, into a different position, a position of the contact in a state in which the thread holding portion of the thread transfer member is moved into a thread holding position.
According to the sixth aspect of the invention, the thread guide device for a sewing machine comprises the contact position determining means. Therefore, it is possible to determine, into a different position, the position of the contact in such a state that the thread holding portion is moved to the thread holding position. Moreover, the holding pressure switching means switches the holding pressure of the thread holding portion based on the position of the contact determined by the contact position determining means.
Accordingly, the position of the contact is determined into the different position by the contact position determining means so that the holding pressure of the thread holding portion in the thread holding position can be regulated into a proper pressure during thread holding. Consequently, it is possible to carry out the thread guiding operation with higher precision.
A seventh aspect of the invention is directed to a thread guide device for a sewing machine comprising thread transfer means including a thread holding portion capable of holding an upper thread and serving to hold the upper thread in a thread holding position by means of the thread holding portion and to transfer the upper thread to the vicinity of a needle eye, and threading means for inserting, into the needle eye, the upper thread transferred to the vicinity of the needle eye by the thread transfer means,
wherein the thread transfer means includes a thread transfer member having the thread holding portion and serving to reciprocate the thread holding portion between the thread holding position and the vicinity of the needle eye by a rotation and a regulating member (a regulating cam 5) for regulating the rotation of the thread transfer member,
the thread transfer member having a first abutment portion (the other end 28b) to abut on the regulating member in the middle in which the thread holding portion goes from the thread holding position to the vicinity of the needle eye, and a second abutment portion (one end 28a) to abut on the regulating member in a position which is more distant from a rotating shaft than a distance from an abutment position of the first abutment portion on the regulating member to the rotating shaft of the thread transfer member in a state in which the thread holding portion is moved to the vicinity of the needle eye.
According to the seventh aspect of the invention, the thread transfer member is provided with the first abutment portion and the second abutment portion. Therefore, the portion of the regulating member which abuts on the first abutment portion can have a size reduced, and furthermore, the regulating member abuts on the second abutment portion in a position placed apart from the center of the rotation of the thread transfer member so that the rotation of the thread transfer member can be regulated stably.
Accordingly, the size of the regulating member can be reduced and the stop position of the thread holding portion in the vicinity of the needle eye can be determined with higher precision. Consequently, it is possible to carry out the thread guiding operation with higher precision.